Magnesium base alloy



Patented Nov. 12, 1940 UNITED STATES MAGNESIUM BASE ALLOY John C. McDonald, Midland, Mich asslgnor to The Dow Chemical Company, Midland, Mich, a corporation of Michigan No Drawing. Application November 13, 1939,

Serial N0. 304,121

4 Claims.

Theinvention relates to magnesium base alloys.

It more particularly concerns alloys of this nature having a high degree of formablity coupled with other improved physical properties, such as high tensile and yield strengths.

5 Magnesium alloys are enjoying increasing use in the structural arts where a light weight metal is desirable, such as for use in making large castings, forgings, and the like. However, the use of these alloys in the rolled form to make sheet metal articles requiring forming operations, such as bending, drawing, and the like, has not progressed as rapidly due to the face that in general alloys of good formability, permitting relatively sharp bends to be made without the 5 article developing external cracks, usually have cent of silver and from 3 to 6 per cent of cadmium. The alloys containing the higher percentages of alloying ingredients, such as from 6 to 10 per cent of silver and from 10 to 14 per cent of cadmium, while still having a suflicient degree of ductility, have exceptionally high yield and tensile properties, and are also'suitable for use in casting operations.

The following table, listing some of the properties of rolled sheet metal made from my new ternary alloy and also the properties of related binary alloys, illustrates the' improvement in yield strength, tensile strength, and ductility or formability, as represented by the per cent increase in elongation, of the new alloy over that of the closely related binary alloys.

inferior characteristics as regards their tensile and yield strengths. Table Nominal composition in percent (magnesium: Annealed Cold rolled remainder) Yield Tensile Percent Yield Tensile Percent Ag Cd strength in strength in elongation strength in strength in elongation lbs/sq. in. lbsJsq. in in 2 inches lbs.lsq. in. lbs./sq. in. in 2 inches 3 20, 000 33,000 is 31,000 07,000 2 a 10, 000 31, 000 7 23, 000 31, 000 2 3 5 18,000 3 000 22 3 000 41,000 2 s 25,000 38,000 10 31,000 44,000 2 8o 12 t 10, 000 31, 000 10 26, 000 32, 000 2 8 12 25,000 41,000 19 42,000 49,000 2 It is, accordingly, the principal object of the invention to provide a magnesium base alloy which may be made into rolled sheet or the like,

possessing a sufficient degree of ductility orformability to be sharply drawn, bent, or otherwise shaped, while having greatly improved tensile and yield strengths.

Other objects and advantages will be apparent as the description of the invention proceeds.

My invention resides in the discovery that a magnesium base alloy composed of from 0.5 to 12 per cent of silver and from 1 to 20 per cent of cadmium, the balance being substantially all magnesium, is endowed with the aforementioned properties. While the properties of improved formability or ductility coupled with high tensile strength and yield strength are manifest over the entire range of composition indicated, I have found that in general the preferred combination of properties, such as the most desirable ductility for forming operations coupled with high tensile strength and greatly increased yield strength, is

obtained when the alloy contains from 1 1:04 per The properties listed in the above table under the section headed by the term annealed were obtained by flrstrolling the alloys at a temperature between about 600 to 800 F., and thereafter annealing them at various temperatures through a temperature range of from 400 to 800 F. The properties selected for the table were those of the annealed specimens which exhibited the maximum elongation. The properties listed under the section headed cold rolled were obtained by subjecting specimens of the alloys which had been hot rolled at a temperature of from 600 to 800 F. to additional rolling in the coldstate, to bring about a total reduc tion of from 2 to 10 per cent. The properties selected for the table were those of the cold rolled specimens which showed the greatest tensile and yield strengths, while having at least a 1 per cent elongation in 2 inches. 1

By comparison of the properties listed in the above table, it will be observed that the combined properties of mynew ternary alloys are always superior to those of the related binary alloys having similar percentages of alloying ingredients. For example, it will be noted that in the lower percentages of alloying ingredients an annealed specimen of the new ternary alloy exhibited better tensile strength and improved elongation over that of the known related parent binary alloys, while the cold rolled specimen of the ternary alloy of the same composition had highly improved tensile and yield strengths over that of the known closely related binary alloy. Similarly in the higher percentage range of alloying ingredients, the properties of the new ternary alloys show improvement over those of the related binary alloys.

While the new alloy is most useful in wrought form, such as sheets, due to its formability characteristics, it may also be suitably used in making castings, forgings, extruded forms, and the like. It is further pointed out that my new alloy is amenable to solution and precipitation heat treatments, which, accordingly, modify its properties.

Mynew ternary alloys may be prepared by any of the methods usually employed for melting and alloying metals with magnesium, such as by adding the respective alloying metals singly or jointly to a bath of molten magnesium which is preferably protected from oxidation by a suitable flux.

I claim:

1. A magnesium base alloy containing from 0.5 to 12 per cent of silver and from 1 to 20 per cent of cadmium, the balance being magnesium.

2. A magnesium base alloycontaining from 1 to 4 per cent of silver and from 3 to 6 per cent of cadmium, the balance being magnesium.

3. A magnesium base alloy containing from 6 to 10 per cent of silver and from 10 to 14 per cent of cadmium, the balance being magnesium.

4. A magnesium base alloy consisting of approximately 3 per cent of silver and 4.5 per cent of cadmium, the balance being magnesium.

JOHN C. McDONALD. 

